Tool coupling with means for centering and clamping

ABSTRACT

The invention relates to a fixing mechanism for a tool for treatment of a material, such as machining. The fixing mechanism comprises a combination of a tool (1), its frame (2) and tool holder (3) in the frame of a machine tool. At least one of the connecting surfaces (r, 7) in the tool frame (2) and in the tool holder (3) in the frame of the machining tool, extending mainly in the mounting direction, is shaped as a curved surface. The first contact surface (6) in connection with the tool frame (2) and the second contact surface (8) in the tool holder (3) are adjusted substantially in a direction perpendicular to the mounting direction, to be placed against each other in the operational position of the fixing mechanism, in order to transmit machining force between the tool frame (2) and the tool holder (3).

THE FIELD OF INVENTION

The invention relates to a fixing mechanism for a tool for treatment ofa material, such as machining, wherein the fixing mechanism comprises acombination of a tool, its frame and tool holder in the frame of amachine tool.

The fixing mechanism according to the invention can be applied in a widerange of technology, including machining by chipping, such as milling,reaming, drilling, turning, etc. of wood, plastics, metal, etc. as thematerial for machining. The fixing mechanism can be used in varioustypes of robot applications for production, in the exchange of grippersor the like in other automatic devices, such as apparatus for transferand treatment of pieces, in pneumatic tools, etc., wherein exchange oftools required for different kinds of operations is necessary forcarrying out various operations.

Further, the above fixing mechanism for a tool is particularlyadvantageous for use in cutting, punching, moulding and forming work,particularly in machining of metal sheets in so-called sheet machiningcenters.

In machining of this kind, the direction of fixing a tool is a linearmovement whereby the machining or forming blade edge directs themachining force to the sheet, usually in a direction perpendicular tothe main direction of the sheet, the sheet being placed between the tooland its counterpart, i.e. a cushion. The tool-fixing mechanism accordingto the invention can be used for fixing both the actual machining tooland its counterpart, i.e. the so-called cushion, to the tool holder inthe frame of the machine tool.

BACKGROUND OF THE INVENTION

According to prior art, it is common to use a so-called conic fit, i.e.a Morse conic fit, for fixing a tool, whereby the tool frame and thetool holder are joined to each other by a fixing movement in their axialdirection, the release being effected in a corresponding manner in theaxial direction. In particular, the conic fit has the disadvantage thatthe connecting surfaces very easily tend to be clamped too much againsteach other, particularly under effect of axial forces. For this reason,many systems presently in use comprise special release mechanisms forreleasing clamped conic surfaces in connection with the exchange of atool. As a natural result, the costs of fixing mechanisms required bytool settings are increased, also, the mechanisms are relatively complexand therefore subject to disturbances during the actual machiningoperation and particularly during the exchange of a tool.

SUMMARY OF THE INVENTION

As to the prior art, reference is further made to the publicationsDE-4218142, EP-22796 and DE-4223158, which disclose tool-fixingmechanisms using interfaces with totally curved surfaces.

It is an aim of the present invention to provide an improved fixingmechanism for a tool, wherein the purpose of the invention is to improvethe prior art in the field for a wide range of applications. Forachieving these aims, the tool-fixing mechanism of the invention isprimarily characterized in that at least one of the connecting surfacesin the tool frame and in the tool holder in the frame of the machiningtool, extending mainly in the mounting direction, is shaped as a curvedsurface and that the first contact surface in connection with the toolframe and the second contact surface in the tool holder are adjusted tobe placed against each other in the operational position of the fixingmechanism, in order to transmit machining force between the tool frameand the tool holder. Using the solution presented above, a very simpleand secure fixing mechanism is achieved. The tool and its frame can beplaced in the tool holder by a very simple movement defined by thecurved surface, wherein the connecting surfaces are placed substantiallyagainst each other and the contact surfaces, extending in a directionsubstantially perpendicular to the mounting direction, in the finalmounting phase transmit the machining force in the mounting directionbetween the tool, the tool frame and the tool holder and/or transmit themachining force by means of a frictional contact in a directionsubstantially perpendicular to the mounting direction.

Some advantageous embodiments of the fixing mechanism according to theinvention are presented in the appended dependent claims.

BRIEF DESCRIPTION OF THE FIGURES

In the following description, the invention will be disclosed withreference to series of figures shown in the appended drawings andillustrating some advantageous embodiments of the fixing mechanismaccording to the invention. In the drawings,

FIG. 1a shows parts of the tool according to the first embodiment,separate in a cross-sectional view in the mounting direction at thebeginning of fixing the tool,

FIG. 1b is a cross-sectional view in the mounting direction, showing thestage of mounting the tool and its frame in connection with the toolholder in the frame of the machine tool,

FIG. 1c is also a cross-sectional view in the mounting direction,showing the tool, the tool frame, and the tool holder in the frame ofthe machine tool in the functional position of the fixing mechanism,

FIG. 1d shows the stage of releasing the tool and the tool frame in theabove-mentioned sectional view,

FIGS. 2a-d show another embodiment of the fixing mechanism,corresponding to the stages shown in FIGS. 1a-d, and

FIGS. 3a-c show essential stages of FIGS. 1a-d of a third embodiment ofthe invention.

DETAILED DESCRIPTION OF THE INVENTION

With reference to FIGS. 1ato 1d, the fixing mechanism comprises as mainparts a tool 1, a tool frame 2 for fixing the tool 1, as well as abushing-like tool holder 3 and clamps 3a. In this embodiment, the tool 1is a cushion or the like, used as a counterpart for a cutting, punching,molding or forming blade.

A connecting element 4 in the tool frame 2 is an inlay with acylindrical shape. It comprises a first connecting surface 5 extendingsubstantially in the mounting direction and being a straight line in themounting direction (arrow A), and further a first contact surface 6,i.e. a bottom surface, joining the first connecting surface and beingsubstantially perpendicular to the mounting direction. In the presentembodiment, the first contact surface 6 is in a ring-like flange partextending from the first connecting surface 5, from its end facing thebottom of the connecting element 4, towards the center line K of thefixing mechanism, wherein, as shown in FIG. 1c, the central openings KR₂and KR₃ of both the tool frame 2 and the holder 3 are equal in size andconcentric, making any movements of additional parts possible inside theholder 3, in the mounting direction.

In the first embodiment illustrated in FIGS. 1a to 1d, the curvilinearconnecting surface, particularly a spherical surface, is a secondconnecting surface 7 in connection with the tool holder 3, extendingfrom a ring-like second contact surface, i.e. a front surface, in adirection perpendicular to the mounting direction A and forming part ofthe outer surface of the tool holder 3, preferably in the mountingdirection. With particular reference to FIG. 1c, the tool frame 2 isarranged to surround the second connecting surface 7 in the end of thetool holder 3, the first 6 and second 8 contact surfaces being againsteach other.

According to the invention, it is advantageous to design the curvilinearsurface, i.e. the second connecting surface 7, in a manner that thedistance between the radius of curvature r of the curvilinear surfaceand the center k located on the center line K of the tool holder 3 inthe mounting direction and the contact surface, i.e. in the presentembodiment the second contact surface 8, fulfills the formula:

    r.sup.2 =D.sup.2 +d.sup.2,

wherein

r=the radius of curvature,

D=the radius of the second contact surface 8 perpendicular to themounting direction A, and

d=the distance between the center of the radius of curvature and thesecond contact surface in the mounting direction A.

Consequently, a curvilinear second connecting surface 7 is formed,extending from the outer edge of the second contact surface 8 at adistance e from the second contact surface in the mounting direction A,being essentially equal to:

    e=2*d,

wherein

d=the distance between the center of the radius of curvature and thesecond contact surface 8 in the mounting direction A.

To make the fixing mechanism function in a compatible manner, thediameter H of the inlay of the connecting element 4 is substantiallyH=2*r, preferably H=2*r+Δ, wherein Δ is the fit used and wherein r issaid radius of curvature.

It is obvious that both the cross-sectional form of the tool holder 3 atleast by the second connecting surface 7 and the cross-sectional form ofthe connecting element 4 in the tool frame 2 in a directionperpendicular to the mounting direction A, is a circular form. The usedfit Δ can be a clearance fit, an interference fit or a pinch fitaccording to the use of the tool.

FIG. 1b shows the mounting of the tool and its frame 1, 2 in the toolholder 3, wherein the tool frame 2 is moved in an inclined position inrelation to the mounting direction A, one edge of the tool holder 3passing the second connecting surface 7 and drawing the tool frame 2towards the tool holder 3 by means of clamps 3a fixed in connection withthe frame 2 (e.g. groove-nose joint 10a, 10b). The rod-like clamps 3aare thus brought to pass the contact surface 8 in order to fix thegroove-nose joint 10a, 10b(FIG. 1a). The tool frame 2 can thus berevolved along the connecting surface 7 forming a spherical curvedsurface to the position shown in FIG. 1c, where the first contactsurface 6 and the second contact surface 8 are in contact with andagainst each other, ready to receive forces in the mounting direction,the clamp 3a effecting a pressure force between the surfaces 6 and 8,wherein also loads (e.g. torsion) in a direction perpendicular to themounting direction can be transmitted due to a frictional contact, i.e.

    F.sub.R =μ*F.sub.K,

wherein

F_(R) =the radial force,

μ=the friction coefficient effective between the surfaces 6 and 8, and

F_(K) =the tractive force of the clamp 3a.

As shown in FIG. 1 d, the tool frame 2 is released in reverse order by apropulsive force F_(K) by the clamps 3a. It should be noted that in thepresent embodiment, the depth s of the inlay of the connecting element 4in the mounting direction A, i.e. the distance between the first contactsurface 6 and the ring-like end surface 9 of the tool frame 2, issubstantially 2*d, wherein d is the distance between the center K of theradius of curvature r and the second contact surface 8 in the mountingdirection A.

The clamps 3a, being two or more clamps surrounding the outer peripheryof the tool frame 2, comprise a nose 10b provided at their ends andextending in the radial direction towards the tool frame 2. A groove 10ais provided on the outer surface of the frame 2 of the tool 13,surrounding the same and functioning as a mounting element, and havingtwo radial surfaces 11a and 11b, each being in co-operation with therespective radial surfaces 12a and 12b of each nose 10b during mountingof the tool, when it is fixed (11a and 12a in FIGS. 1 a-c) as well asduring release (11b and 12b in FIG. 1 d).

Alternatively, with reference to FIG. 2, the fixing mechanism accordingto the invention can be arranged so that a curvilinear surface, seen ina direction perpendicular to the mounting direction, is formed on theouter surface of the tool frame 2, which is spherical substantially inthe mounting direction, wherein the connecting element 4 in the toolholder is a corresponding inlay. Naturally, it is possible to shape bothconnecting surfaces at least partly curved.

In the embodiment of FIG. 2, the tool frame 2 comprises a tool fixingelement 2a, the tool 1 being fixed on the first surface of the same. Thesecond surface of the plate-like fixing element 2a forms partly thefirst contact surface 6, against which, in turn, a connecting surfaceelement 2b is fixed, whose surface in the mounting direction forms thecurved connecting surface 7. The connecting surface element 2b is placedcentrally in relation to the first contact surface 6, wherein theconnecting surface element 2b is surrounded by the first contact surface6 in a ring-like manner. In the mounting direction A, a mounting element13 extends from the connecting surface element, comprising a central arm13a substantially in the mounting direction, and an extension element13b at its free end.

The tool holder 3 is at its end provided with a flange-like extension,its end surface forming the second contact surface 8. The tool holder 3is like a bushing, wherein a clamp 3a is arranged to be movable insidethe bushing hole in the mounting direction, receiving a guiding effectfrom the internal hole of the bushing form of the tool holder 3. Thefree end of the clamp 3a is provided with an opening-groove system 14,with an opening 14a arranged in the mounting direction to receive thearm 13a of the mounting element 13 as shown in FIG. 2a, wherein theclamp 3a is in the outer position, and the end of the opening-groovesystem 14 protrudes in the mounting direction A outside the secondcontact surface 8, wherein the mounting element 13 of the frame 2 can bemounted e.g. from the side in connection with the groove-opening system14 so that its extension element 13b is placed inside a groove element14b. The groove element 14b comprises radial surfaces 12a, 12b at theends of the groove element 14b, perpendicular to the mounting directionA. Thus, according to FIG. 2b, the tool 1 with its frame 2 can beattracted towards the tool holder 3, wherein the connecting surfaceelement 2b is placed inside the bushing form of the holder 3, the innersurface of the same near the end forming thus the second connectingsurface 5. The first radial surface 11a of the extension element 13b isat the mounting stage in contact with the first radial surface 12a ofthe groove element 14. The mounting is effected in a manner presented inconnection with blank 1, resulting in a situation shown in FIG. 2c,where in the fixing shown in FIG. 2c, the clamp 3a is driven by a forceF_(K) directed upwards, the contact surfaces 6 and 8 being against eachother. The tool 1 is released from the holder in a manner shown in FIG.2d, wherein the second radial surfaces 11b and 12b of elements 13 and 14are against each other and the force of the clamp 3a effective in themounting direction removes the contact surface element 2 from thebushing form of the clamp 3a substantially in the mounting direction A.

With reference to FIG. 3, the frame 2 is fixed to the clamp 3a by meansof a ball mechanism 15 or the like placed in the radial direction insidea series of openings 3b in the clamp 3a, wherein at the starting andreleasing stages, shown in FIGS. 3a and 3c, the balls 15a or the likecan be placed in inlays 16 in the bushing hole of the holder, being thusmoved outwards in the radial direction and making it possible for theextension element 13b of the mounting element 13 to pass the balls 15ain the mounting direction A. In the bushing hole of the holder 3, abushing-like tube forming the clamp 3a is arranged to be movable in themounting direction A, wherein the mounting of the frame 2 can be starteddirectly according to FIG. 3a by inserting the mounting element 13,including the arm element 13a and the extension element 13b, in themounting direction A inside the tube form of the clamp 3a, the balls 15abeing in connection with the inlays 16 and thus in their outermostposition in the plane of the inner surface of the tube form. When theclamp 3a is moved upwards in relation to the holder 3, as shown in FIG.3b, the balls 15a are placed inside in a direction perpendicular to themounting direction A and forced in connection with the radial surface11a of the extension element 13b by the surface of the inner hole of theholder 3, in order to lock and effect the force F_(K) to the frame 2 ina manner corresponding to that explained above in connection with FIGS.1 and 2. The frame 2 is released as shown in FIG. 3c by using the facesurface 3c of the clamp 3a (corresponding to the radial surface 12b inFIG. 2) to push the contact surface 6 of the connecting surface element2b which thus forms the second radial surface 11b. The connectingsurface 5 in the holder 3 is formed in the connecting element 4 whichhas a diameter exceeding the bushing hole of the holder 3 where theclamp 3a is movable. Consequently in the embodiment according to FIG. 3,the structure corresponding to the groove-opening system 14 (FIG. 2) isformed to be adjusted in the radial direction according to the movementof the clamp 3a, instead of the solid structure of FIG. 2.

We claim:
 1. In combination, a fixing mechanism for a tool for treating a material including machining said material, comprising:a machine tool; a tool frame for said tool; and a tool holder; wherein said tool frame and said tool holder comprise respective connecting surfaces extending substantially along a mounting direction, said tool frame including a first contact surface and said tool holder including a second contact surface, said first and second contact surfaces being oriented substantially in a direction perpendicular to the mounting direction and to be placed against each other when said tool is in operation for transmitting machining force between said tool frame and said tool holder; and wherein at least one of said connecting surfaces being shaped as a spherical surface.
 2. Fixing mechanism according to claim 1, wherein said connecting surfaces and said contact surfaces are joined substantially together at their respective edges in both said tool frame and said tool holder.
 3. Fixing mechanism according to claim 1, wherein said spherical surface is formed on the outer surface of said tool holder to extend from the outer edge of said second contact surface; andwherein said tool frame comprises a connecting element, said connecting element being a recess.
 4. Fixing mechanism according to claim 1, wherein said spherical surface is formed on the outer surface of said tool frame; andwherein said tool holder comprises a connecting element, said connecting element being a recess.
 5. Fixing mechanism according to claim 1, wherein the length of the radius of curvature of said spherical surface and the distance between the center (K) of said radius and said second contact surface are calculated according to the formula

    r.sup.2 =D.sup.2 +d.sup.2,

where r=the radius of curvature, D=the radius of said second contact surface perpendicular to the mounting direction (A), and d=the distance between the center of the radius of curvature and the contact surface in the mounting direction (A).
 6. Fixing mechanism according to claim 3, wherein the diameter (H) of an inlay of said connecting element is substantially 2*r, and preferably (H)=2*r+A, where r is said radius of curvature of said spherical surface and A is the fit used, such fit including a clearance fit, an interference fit or a pinch fit.
 7. Fixing mechanism according to claim 4, wherein the diameter (H) of an inlay of said connecting element is substantially 2*r, and preferably (H)=2*r+A, where r is said radius of curvature of said spherical surface and A is the fit used, such fit including a clearance fit, an interference fit or a pinch fit.
 8. Fixing mechanism according to claim 1, wherein said spherical surface extends from said first contact surface in the mounting direction (A) substantially at a distance (e), where (e) is approximately 2*d, and d=the distance from the center of the radius of curvature to the face surface in the mounting direction (A).
 9. Fixing mechanism according to claim 3, wherein said connecting element is a recess with a substantially cylindrical shape whose depth from said second contact surface in the mounting direction (A) is substantially 2*d, where d=the distance between the center (K) of the radius (r) of curvature and said second contact surface in the mounting direction (A).
 10. Fixing mechanism according to claim 4, wherein said connecting element is a recess with a substantially cylindrical shape whose depth from the second contact surface in the mounting direction (A) is substantially 2*d, where d=the distance between the center (K) of the radius (r) of curvature and said second contact surface in the mounting direction (A).
 11. Fixing mechanism according to claim 1, wherein said tool frame comprises:a fixing element in which said tool is fixed; a connecting surface element, placed on the opposite side of said fixing element relative to said tool, having a spherical connecting surface, the contact surface of said fixing element surrounding said connecting surface element; and a mounting element arranged in co-operation with a groove-opening arrangement of a fixing means placed in said holder, said fixing means being movable relative to said holder.
 12. Fixing mechanism according to claim 1, wherein said mounting element protrudes from the connecting surface element and comprises an arm element and an extension element. 